R.ARY 
OF   THE 

U  N  IVLR.SITY 
OF    ILLINOIS 


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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station, 


URBANA,  DECEMBER,   1902. 


BULLETIN  NO.  82. 


METHODS  OF  CORN  BREEDING.* 


BY  CYKIL  GEORGE   HOPKINS,  PH.    D.,   PROFESSOR   OF   AGRONOMY   IN   THE 

AGRICULTURAL  COLLEGE  AND  CHIEF  IN  AGRONOMY  AND  CHEMISTRY 

IN  THE  AGRICULTURAL  EXPERIMENT  STATION. 


It  is  a  well  established  fact  that  there  now  exist  markets  and 
demands  for  different  kinds  of  corn. 

The  price  of  corn  varies,  say,  from  >£  cent  to  1  cent  per  pound. 

The  cost  of  protein  in  the  principal  stock  feeding-  states  varies 
from  3  to  5  cents  per  pound.  In  other  words,  the  protein  is  several 
times  more  valuable  per  pound  than  corn  itself.  Consequently, 
stock  feeders  want  more  protein  in  corn.  (Very  possibly  the  feed- 
ers in  the  southern  states  want  more  carbohydrates  to  supplement 
their  present  more  abundant  supplies  of  nitrogenous  food  stuffs.) 

The  price  of  corn  starch  varies  from  2  or  3  cents  to  5  or  even 
10  cents  per  pound,  depending-  upon  the  wholesale  or  retail  nature 
of  the  sale.  The  manufacturers  of  starch  and  of  g-lucose  sug-ar, 
glucose-syrup,  and  other  products  made  from  starch  want  more 
starch  in  corn. 

*Read  before  the  Section  on  Agriculture  and  Chemistry  of  the  Associa- 
tion of  American  Agricultural  Colleges  and  Experiment  Stations,  at  Atlanta, 
Georgia,  October  8,  1902;  and  before  the  Illinois  Live  Stock  Breeders' Associa- 
tion, at  Bloomington,  Illinois,  November  20,  1902. 

525 


526  BULLETIN  NO.  82.  [  December, 

In  its  own  publication  a  large  commercial  concern,  which  uses 
enormous  quantities  of  corn,  makes  the  following1  statements: 

"A  bushel  of  ordinary  corn,  weighing-  56  pounds,  contains 
about  4^2  pounds  of  germ,  36  pounds  of  dry  starch,  7  pounds  of 
gluten,  and  five  pounds  of  bran  or  hull,  the  balance  in  weight  be- 
ing made  up  of  water,  soluble  matter,  etc.  The  value  of  the  germ 
lies  in  the  fact  that  it  contains  over  40  per  cent,  of  corn  oil,  worth, 
say,  5  cents  per  pound,  while  the  starch  is  worth  \%  cents,  the 
gluten  1  cent,  and  the  hull  about  YZ  cent  per  pound. 

"It  can  readily  be  seen  that  a  variety  of  corn  containing,  say 
one  pound  more  oil  per  bushel  would  be  in  large  demand. 

"Farmers  throughout  the  country  do  well  to  communicate 
with  their  respective  agricultural  experiment  stations  and  secure 
tneir  cooperation  along  these  lines." 

These  are  statements  and  suggestions  which  should,  and  do, 
attract  the  attention  of  experiment  station  men.  They  are  made 
by  the  Glucose  Sugar  Refining  Company  of  Chicago,  a  company 
which  purchases  and  uses,  in  its  six  factories,  about  fifty  million 
bushels  of  corn  annually.  According  to  these  statements,  if  the  oil  of 
corn  could  be  increased  one  pound  per  bushel,  the  actual  value  of 
the  corn  for  glucose  factories  would  be  increased  5  cents  per  bushel; 
and  the  President  of  the  Glucose  Sugar  Refining  Company  has 
personally  assured  the  writer  that  his  company  would  be  glad  to 
pay  a  higher  price  for  high  oil  corn  whenever  it  can  be  furnished 
in  large  quantities.  The  increase  of  five  cents  per  bushel  on  fifty 
million  bushels  would  add  $2,500,000  to  the  value  of  the  corn  pur- 
chased by  this  one  company  each  year.  The  Glucose  factories  are 
now  extracting  the  oil  from  all  the  corn  they  use  and  are  unable 
to  supply  the  market  demand  for  corn  oil.  On  the  other  hand,  to 
these  manufacturers,  protein  is  a  cheap  by-product  and  conse- 
quently they  want  less  protein  in  corn. 

Corn  with  a  lower  oil  content  is  desired  as  a  feed  for  bacon 
hogs,  especially  for  our  export  trade,  very  extensive  and  thorough 
investigations  conducted  in  Germany  and  Canada  having  proved 
conclusively  that  ordinary  corn  contains  too  much  oil  for  the  pro- 
duction of  the  hard  firm  bacon  which  is  demanded  in  the  markets 
of  Great  Britain  and  Continental  Europe. 

The  methods  of  corn  breeding  devised  by  the  Illinois  Experi- 
ment Station  and  now  used  not  only  by  us,  but  also  by  the  Illinois 
Seed  Corn  Breeders'  Association,  and,  to  some  extent,  by  other  Ex- 
periment Stations  and  other  corn  breeders,have  for  their  object  the 
improvement  of  corn — in  yield  and  in  quality.  In  the  main  the 
methods  are  now  the  same  as  we  have  employed  for  the  past  six 


METHODS   OF  CORN   BREEDING.  527 

years  and  they  have  given  results  which  enable  us  to  assert  with 
confidence  that  by  these  methods  corn  can  be  improved  in  a  very 
marked  degree  and  for  many  different  purposes.  The  yield  of  corn 
can  be  increased,  and  the  chemical  composition  of  the  kernel  can 
be  changed  as  may  be  desired,  either  to  increase  or  to  decrease  the 
protein,  the  oil,  or  the  starch. 

Following-  is  a  brief  description  of  the  methods  of  corn  breed- 
ing- which  we  practice  and  which  we  have  recommended  to  others: 

PHYSICAL  SELECTION  OF  SEED  CORN. 

The  most  perfect  ears  obtainable  of  the  variety  of  corn  which 
it  is  desired  to  breed  should  be  selected.  These  ears  should  con- 
form to  the  desirable  standards  of  this  variety  and  should  possess 
the  principal  properties  which  belong-  to  perfect  ears  of  corn,  so  far 
as  they  are  known  and  as  completely  as  it  is  possible  to  secure 
them.  These  physical  characteristics  and  properties  include  the 
leng-th,  circumference,  and  shape  of  the  ear  and  of  the  cob;  the 
number  of  rows  of  kernels  and  the  number  of  kernels  in  the  row; 
the  weig-ht  and  color  of  the  grain  and  of  the  cob;  and  the  size  and 
shape  of  the  kernels.  In  making-  this  selection  the  breeder  may 
have  in  his  mind  a  perfect  ear  of  corn  and  make  the  physical  se- 
lection of  seed  ears  by  simple  inspection,  or  he  may  make  absolute 
counts  and  measurements  and  reduce  the  physical  selection  almost 
to  an  exact  or  mathematical  basis. 

In  this  connection  let  me  suggest  that  there  is  some  dang-er  of 
corn  breeders  making-  too  much  of  what  might  be  called  fancy 
points  in  selecting-  seed  ears.  We  should  learn  the  facts  which  are 
facts  and  not  base  our  selections  too  much  upon  mere  ideas  and 
opinions.  For  example,  it  is  not  known  that  ears  whose  tips  are 
well  filled  and  capped  with  kernels  are  the  best  seed  ears.  Indeed 
it  is  not  improbable  that  the  selection  of  such  seed  ears  will  cause 
the  production  of  shorter  ears  and  a  reduced  yield  per  acre.  It  is 
true  that  the  percentag-e  of  shelled  corn  from  a  given  ear  is  the 
greater,  the  greater  the  proportion  of  corn  to  the  cob,  but  our  inter- 
est in  that  percentage  is  very  slight  compared  to  that  of  yield  per 
acre,  and  perhaps  for  the  greatest  possible  yield  of  shelled  corn 
per  acre  it  requires  that  the  ears  shall  have  good  sized  cobs.  Pos- 
sibly the  corn  which  shall  untimately  surpass  all  others  for 
yield  per  acre  will  have  tapering  and  not  cylindrical  ears.  These 
are  some  of  the  points  regarding  which  men  have  some  ideas  and 
opinions  but  as  yet  we  have  no  definite  facts,  and  we  shall  need 
several  years  more  to  obtain  absolute  knowledge  regarding  some 
of  these  points.  Let  us  base  our  selections  of  seed  corn  first  upon 


528 


BULLETIN   NO.   82. 


[December, 


known  facts  and  performance  records,  and  secondly  upon  what  one 
may  call  his  "type"  of  corn. 

CHEMICAL  SELECTION  BY  MECHANICAL  EXAMINATION. 
The  selection  of  seed  ears  for  improved  chemical  composition 
by  mechanical  examination  of  the  kernels  is  not  only  of  much  as- 
sistance to  the  chemist  in  enabling-  him  to  reduce  greatly  the  chem- 
ical work  involved  in  seed  corn  selection,  but  it  is  of  the  greatest 
practical  value  to  the  ordinary  seed  corn  grower  who  is  trying1  to 
improve  his  seed  corn  with  very  limited  service,  if  any,  from  the 
analytical  chemist.  This  chemical  selection  of  seed  ears  by  me- 
chanical examination,  as  well  as  by  chemical  analysis  (which  is 
described  below),  is  based  upon  two  facts: 

1.  That  the  ear  of  corn  is  approximately  uniform  throughout 
in  the  chemical  composition  of  its  kernels. 

2.  That  there  is  a  wide  variation  in  the  chemical  composition 
of  different  ears,  even  of  the  same  variety  of  corn.     These  two  facts 
are  well  illustrated  in  Table  1. 

TABLE  I.    PROTEIN  IN  SINGLE  KERNELS. 


Ear  A, 
protein, 
per   cent. 

Ear   B, 
protein, 
per   cent. 

Ear  C, 
protein, 
per  cent. 

Ear   D, 
protein, 
per  cent. 

Kernel  No.  i  

12.46 

II  .  "iS 

7-4S 

8.72 

Kernel  No.  2  

12.  ;4 

12.^2 

7.  54 

8.41 

Kernel  No.  3  

12.44 

12.  10 

7.6o 

8.73 

Kernel  No.  4  

12.  SO 

12.  Cd 

7  47 

8.31 

Kernel  No.  5  

I2.3O 

12    14. 

7  74 

8  02 

Kernel  No.  6  

1  2.  4Q 

12.  OS 

8.70 

8.76 

Kernel  No.  7  

12.  t;o 

12   84 

8.46 

8  80 

Kernel  No.  8  

12.  14 

* 

8  60 

o  02 

Kernel  No.  9  

12    14 

12   O4 

8  86 

8  96 

Kernel  No.  10  

12   71 

12   7S 

8  10 

8  89 

It  will  be  observed  that,  while  there  are,  of  course,  small  dif- 
ferences among-  the  different  kernels  of  the  same  ear,  yet  each  ear 
has  an  individuality  as  a  whole,  the  difference  in  composition  be- 
tween different  ears  being-  much  more  marked  than  between  differ- 
ent kernels  of  the  same  ear. 

The  uniformity  of  the  individual  ear  makes  it  possible  to  esti- 
mate or  to  determine  the  composition  of  the  corn  by  the  examina- 
tion or  analysis  of  a  few  kernels.  The  remainder  of  the  kernels 
on  the  ear  may  then  be  planted  if  desired.  The  wide  variation  in 
the  composition  between  different  ears  furnishes  a  starting  point 
for  the  selection  of  seed  in  any  of  the  several  different  lines  of  de- 
sired improvement. 

The  methods  of  making-  a  chemical   selection  of  ears  of  seed 

*Determination  lost  by  accident. 


1902.] 


METHODS   OF   CORN   BREEDING. 


529 


HIGH-PROTEIN 
KERNELS 

(little  starch) 


LOW-PROTEIN 
KERNELS 

(much  starch) 


PLATE  i. 

corn  by  a  simple  mechanical  examination  of  the. "kernels  is  based 
upon  the  fact  that  the  kernel  of  corn  is  not  homogenous  in 
structure,  but  consists  of  several  distinct  and  readily  observable 
parts  of  markedly  different  chemical  composition.  (See  illustra- 
tions.) Aside  from  the  hull  which  surrounds  the  kernel,  there  are 
three  principal  parts  in  a  grain  of  corn: 

1.  Tne  darker  colored  and  rather  hard  and  horny  layer  lying 
next  to  the  hull,  principally  in  the  edges  and   toward  the  tip  end 
of  the  kernel,  where  it  is  about  3  millimeters,  or  y%  of  an  inch,  in 
thickness. 

2.  The  white,  starchy-appearing  part  occupying  the  crown 
end  of  the  kernel  and  usually  also  immediately  surrounding,  or 
partially  surrounding,  the  germ. 


530 


BULLETIN  NO.  82. 


[  December, 


HIGH-OIL 
KERNELS 

(large  germs) 


LOW-OIL 

KERNELS 

(small  germs) 


PLATE  2. 

3.  The  germ  itself  which  occupies  the  central  part  of  the 
kernel  toward  the  tip  end. 

These  different  parts  of  the  corn  kernel  can  be  readily  recog- 
nized by  merely  dissecting-  a  single  kernel  with  a  pocket  knife,  and 
it  may  be  added  that  this  is  the  only  instrument  needed  by  any- 
body in  making  a  chemical  selection  of  seed  corn  by  mechanical 
examination. 

The  horny  layer  which  usually  constitutes  about  65  per  cent, 
of  the  corn  kernel  contains  a  large  proportion  of  the  total  protein 
in  the  kernel. 

The  white,  starchy  part  constitutes  about  20  per  cent,  of  the 


IQO2.]  METHODS   OF   CORN   BREEDING.  531 

whole  kernel,  and  contains  a  small  proportion  of  the  total  protein. 
The  germ  constitutes  only  about  10  per  cent,  of  the  corn  kernel, 
but,  while  it  is  rich  in  protein,  it  also  contains  more  than  85  per 
cent,  of  the  total  oil  content  of  the  whole  kernel,  the  remainder  of 
the  oil  being1  distributed  in  all  of  the  other  parts. 

By  keeping1  in  mind  that  the  horny  layer  is  larg-e  in  propor- 
tion and  also  quite  rich  in  protein  and  that  the  germ,  althoug-h 
rather  small  in  proportion  is  very  rich  in  protein,  so  that  these  two 
parts  contain  a  very  larg-e  proportion  of  the  total  protein  in  the 
corn  kernel,  it  will  be  readily  seen  that  by  selecting  ears  whose 
kernels  contain  more  than  the  average  proportion  of  g-erm  and 
horny  layer  we  are  really  selecting  ears  which  are  above  the 
average  in  their  protein  content.  As  a  matter  of  fact,  the  method 
is  even  more  simple  than  this,  because  the  white  starchy  part  is 
approximately  the  complement  of,  and  varies  inversely  as,  the  sum 
of  the  other  constituents;  and  to  pick  out  seed  corn  of  high 
protein  content  it  is  only  neccessary  to  select  those  ears  whose  ker- 
nels show  a  relatively  small  proportion  of  the  white,  starchy  part 
surrounding  the  germ. 

As  more  than  85  per  cent,  of  the  oil  in  the  kernel  is  contained 
in  the  germ,  it  follows  that  ears  of  corn  are  relatively  high  or  low 
in  their  oil  content,  according  as  their  kernels  have  a  larger  or 
smaller  proportion  of  germ. 

In  selecting  seed  corn  by  mechanical  examination  for  improve- 
ment in  composition  we  remove  from  the  ear  a  few  average  kernels; 
cut  two  or  three  of  these  kernels  into  cross  sections  4and.  two  or 
three  other  kernels  into  longitudinal  sections  and  examine  these 
sections  as  they  are  cut,  usually  simply  with  the  naked  eye. 

If  we  are  selecting  seed  ears  for  high  protein  content  we  save 
those  ears  whose  kernels  show  a  small  proportion  of  the  white 
starch  immediately  adjoining  or  surrounding  the  germ.  If  se- 
lecting corn  for  low  protein  content  we  look  for  a  larger  propor- 
tion of  white  starch  surrounding  the  germ.  Our  results  have 
shown  that  the  white  starch  in  this  position,  that  is,  surrounding 
the  germ  toward  the  tip  end  of  the  kernel,  is  a  better  index  of  the 
protein  content  than  the  starch  in  the  crown  end. 

If  we  are  selecting  seed  ears  for  high  oil  content  we  save  those 
ears  whose  kernels  show  a  large  proportion  of  firm  and  solid  germ; 
while  if  seed  of  low  oil  content  is  desired,  we  look  for  a  small  pro? 
portion  of  germ  in  the  kernel. 

It  should  be  emphasized  that  it  is  not  the  absolute,  but  propor- 
tionate, size  or  quantity  of  germ  or  of  white  starch  which  serves  as 
a  guide  in  making  these  selections. 


532  BULLETIN  NO.  82.  [December, 

CHEMICAL  SELECTION  BY  CHEMICAL  ANALYSIS. 

In  selecting1  seed  corn  by  chemical'  analysis  we  remove  from 
the  individual  ear  two  adjacent  rows  of  kernels  as  a  representative 
sample.  This  sample  is  ground  and  analyzed  as  completely  as  may 
be  necessary  to  enable  us  to  decide  whether  the  ear  is  suitable  for 
seed  for  the  particular  kind  of  corn  which  it  is  desired  to  breed. 
Dry  matter  is  always  determined  in  order  to  reduce  all  other  determ- 
inations to  the  strictly  uniform  and  comparable  water-free  basis. 
If,  for  example,  we  desire  to  change  only  the  protein  content,  then 
protein  is  determined.  If  we  are  breeding1  to  change  both  the  pro- 
tein and  the  oil,  then  determinations  of  both  of  these  constituents 
must  be  made. 

For  a  satisfactory  breeding1  plot,  about  20  to  40  selected  seed 
ears  are  required.  If  the  breeder  desires  to  make  only  physical 
improvement  then  he  should  select,  say,  40  of  the  most  nearly  per- 
fect ears  which  it  is  possible  to  pick  out  by  inspection  or  by  exact 
physical  measurements.  If  it  is  desired  to  improve  the  composition 
or  quality  of  the  corn  as  well  as  the  physical  properties,  then  at 
least  200  physically  perfect  ears  should  be  selected,  and,  from  these 
200  ears,  the  40  ears  which  are  most  suitable  as  seed  for  the  partic- 
ular kind  of  corn  which  it  is  desired  to  breed  should  be  selected, 
either  by  mechanical  examination  of  sections  of  kernels,  which  any- 
body can  make,  or  by  chemical  analysis,  or  by  a  combination  of 
these  two  methods.  In  our  own  work  we  now  commonly  select  by 
physical  inspection  or  measurement  the  200  ears;  then,  from  these 
200  ears,  we  select  by  mechanical  examination  of  sections  of  ker- 
nels the  best  50  or  100  ears,  and  from  this  lot  we  finally  select  by 
chemical  analysis  the  best  20  to  40  seed  ears  for  planting1.  This 
combination  of  methods  effects  a  very  satisfactory  seed  selection 
and  requires  only  one-half  as  much  chemical  work  as  would  be  re- 
quired if  the  method  of  chemical  analysis  alone  were  employed. 

Table  2  shows  very  fairly  the  degree  of  seed  improvement 
which  may  be  accomplished  by  these  different  methods  of  selection, 
when  breeding1  to  change  only  the  protein  content  of  corn. 

It  may  be  stated  that  equally  satisfactory  results  may  be  ob- 
tained in  chemical  selection  by  mechanical  examination  for  secur- 
ing1 seed  ears  of  hig-h  or  low  oil  content.  For  example,  the  writer 
has  selected  by  mechanical  examination,  from  a  lot  of  272  ears  of 
corn,  18  ears  for  high  oil  content  which  averaged  5.24  per  cent,  of 
oil;  and,  from  the  same  lot  of  corn,  30  ears  were  selected  for  low 
oil  content  which  averaged  4.13  per  cent,  oil,  making  an  average 
difference  of  1.11  per  cent,  of  oil. 


1902.] 


METHODS   OF    CORN    BREEDING. 


533 


TABLE  2.      SOME  FAIR  ILLUSTRATIONS  OF  ACTUAL   RESULTS    OBTAINED    IN 
SELECTION  OF  SEED  CORN. 
(Protein,  average  per  cent.) 


Variety 

200 
average 
seed  ears. 

50  ears 
selected  by 
mechanical 
examination. 

28  ears 
selected  by 
chemical 
analysis. 

10 
best 
seed 
ears. 

Best 
single 
seed 
ear. 

Silver  Mine 

10  oo 

9.47 

8.77 

7.97 

7.00 

Boon  County  White.  . 
Learning     

10.57 
ii  .96 

9.72 
II  .36 

9-36 
10.79 

8.84 
10.08 

8.69 
8.82 

Learning   i 

ii  .96 

12.44 

13.33 

14.03 

14-63 

Learning  

ii  .27 

11.84 

12.43 

13.  12 

14.71 

Yellow  Dent  

11.14 

ii  .64 

12.  II 

12.55 

13.24 

Riley's  Favorite  

ii  .02 

11.^8 

12.41 

12.99 

15.78 

Burr's  White  

12.48* 

12.88 

14.36 

14.87 

15.71 

Burr's  White             .  ,, 

9.2Ot 

9.  10 

7-77 

7.56 

7.08 

Learning     

II  .26 

12.  14! 

Learning  

II  .26 

10.67$ 

*  Average  protein  content  of  ten  field  rows  of  Burr's  White  after  four  years' 
breeding  for  high  protein. 

|  Originally  from  same  stock  of  Burr's  White  as  preceding,  but  bred  four 
years  for  low  protein. 

J  Two  lots  of  42  ears  each  selected  from  the  same  lot  of  200  ears  for  two  breeding 
plots,  high  protein  and  low  protein,  the  seed  for  which  is  selected  by  physical 
inspection  and  mechanical  examination  but  without  chemical  analysis  of  individ- 
ual ears. 

If  the  method  of  mechanical  examination  alone  is  employed  in 
making-  the  chemical  selection,  then,  if  possible,  there  should  be 
some  chemical  control  of  the  work,  at  least  until  the  breeder  has 
become  sufficiently  skilled,  or  has  had  sufficient  experience,  to  feel 
that  he  knows  how  to  make  a  chemical  selection  of  seed  ears  by 
mechanical  examination  of  kernels.  Such  a  chemical  control  does 
not  involve  a  large  amount  of  chemical  work.  In  Illinois  the  Ex- 
periment Station  offers  such  a  chemical  control  to  farmers  who  will 
agree  to  make  the  selection  of  the  best  possible  seed,  both  by  phys- 
ical inspection  of  ears  and  mechanical  examination  of  kernels  and 
who  will  further  agree  to  secure  data  and  breed  the  corn  in  accord- 
ance with  our  directions. 

This  control  is  affected  by  analyzing-  only  two  samples  of  corn 
each  year;  one  composite  sample  of  the  rejected  ears,  five  averag-e 
kernels  being-  taken  from  each  ear,  and  one  composite  sample  of  the 
20  to  40  selected  seed  ears,  twenty  averag-e  kernels  being-  taken  from 
each  of  these  ears,  and  each  of  these  two  composite  samples  being- 
properly  labeled  and  analyzed. 

One  of  the  best  selections  which  has  yet  been  made  by  mechan- 
ical examination  was  accomplished  last  spring-  by  a  farmer  who  is 
breeding-  corn  for  higher  protein  content.  Out  of  a  lot  of  165  ears 


534 


BULLETIN    NO.    82. 


[December, 


of  corn  he  selected  15  ears  whose  protein  content  averaged  1.48  per 
cent,  higher  than  that  of  the  150  rejected  ears,  as  was  determined 
by  the  chemical  analysis  of  a  composite  sample  from  each  of  the 
two  lots.  Because  of  the  chemical  control  which  the  Station 
affords  him,  he  knows  each  year  just  how  much  he  has  accom- 
plished. 

If  the  purpose  of  breeding-  a  kind  of  corn  is  principally  to 
change  its  content  of  a  single  constituent,  as  to  increase  protein, 
then  the  selection  of  the  best  40  ears  is  simple  and  regular  by  either 
method;  but  if  it  is  desired  to  effect  changes  in  the  content  of  two 
constituents,  as  to  increase  the  protein  and  to  increase  the  oil  in 
the  same  corn,  then  one  could  hardly  expect  to  make  much  progress 
in  both  directions,  if  he  relied  solely  upon  mechanical  examination 
of  kernels  for  chemical  selection  of  seed  ears.  Even  after  the 
chemical  analyses  of  100  ears  have  been  made  it  requires  some  com- 
putation to  determine  which  are  really  the  best  40  ears.  For  ex- 
ample, an  ear  may  be  desirable  for  seed  because  of  its  high  protein 
content,  but  it  may  not  be  sufficiently  high  in  oil.  In  order  to  re- 
duce the  selection  to  an  exact  basis,  we  have  adopted  simple  math- 
ematical computations  for  all  such  cases. 

For  high  protein  and  high  oil  in  the  same  corn,  we  multiply 
the  percentage  of  protein  by  the  percentage  of  oil  and  use  the 
product  as  the  selection  coefficient,  the  forty  highest  products  des- 
ignating the  forty  best  ears. 

For  low  protein  and  low  oil  we  multiply  the  percentages  to- 
gether and  use  the  lowest  product  as  the  selection  coefficient. 

For  high  protein  and  low  oil  in  the  same  corn,  we  divide  the 
percentage  of  protein  by  the  percentage  of  oil  and  use  the  highest 
quotients  as  our  selection  coefficients. 

TABLE  3.    SELECTION  OF  SEED  CORN    FOR  HIGH  PROTEIN  AND    HIGH    OIL. 


No.  Ear 

Protein 
in  corn. 

Oil 
in  corn. 

Selection 
coefficient- 

I  

11.17 

6.03 

67.30 

2  

12.66 

4.90 

62.00 

3  

13.60 

4.92 

66.89 

4  

10.85 

4-55 

49.89 

5  •  • 

I  I    OI 

<?.72 

62.97 

6  ::::::::::;;:::;:;:::::;:;;::;:::: 

1  1  .  t;o 

4.77 

54.81 

7  

14.71 

5.56 

81.75 

8  

IO.O7 

4.7^ 

-17  62 

o.  . 

17.11 

^.44 

71.53 

10  

10.  19 

q   80 

CQ    IO 

ii  

ii  .01 

^.07 

65.78 

12  

10.30 

4.7^ 

in    IT. 

13.  . 

IV  06 

5.28 

73.72 

Average  

11.87 

^.26 

62  =;o 

1902.]  METHODS   OF   CORN   BREEDING.  535 

For  low  protein  and  high  oil  we  divide  in  the  same  manner, 
but  use  the  lowest  quotients  for  selecting-  the  best  ears. 

Table  3  illustrates  the  value  of  this  method  as  applied  to  the 
selection  of  the  best  seed  ears  for  both  high  protein  and  high  oil. 

It  will  be  observed  that  some  ears  which  are  high  in  only  one 
desirable  constituent  (see  No.  2  and  No.  10)  must  be  discarded  be- 
cause the  selection  coefficients  which  they  give  are  even  below  the 
average;  while  other  ears  which  may  be  quite  low  in  one  constit- 
uent (see  No.  1  and  No.  3)  still  furnish  acceptable  selection  coffi- 
cients. 

THE  BREEDING  PLOT. 

The  40  selected  seed  ears  are  planted  in  40  separate  parallel 
rows,  one  ear  to  a  row,  consequently  the  breeding  plot  should  be  at 
least  40  corn  rows  wide  and  long  enough  to  require  about  three- 
fourths  of  an  ear  to  plant  a  row.  It  is  well  to  shell  the  remainder 
of  the  corn  from  all  of  the  40  ears,  mix  it  together,  and  use  it  to 
plant  a  border  several  rows  wide  entirely  around  the  breeding-  plot, 
to  protect  it,  especially  from  foreign  pollen. 

In  my  judgement  one  of  the  most  practical  and  satisfactory 
locations  for  the  breeding  plot  is  in  a  larger  field  of  corn  planted 
with  seed  which  is  as  nearly  as  possible  of  the  same  breeding  as 
that  planted  in  the  breeding  plot  itself.  The  stock  seed  for  this 
field  should  always  be  selected  from  the  previous  year's  breeding 
plot  and  it  may  well  include  as  many  of  the  160  rejected  ears  as 
are  known  to  be  above  the  average  of  the  200.  Or,  if  the  breeding 
plot  can  be  well  isolated  from  all  other  corn  fields  and  still  occupy 
good  soil,  this  also  makes  a  very  suitable  location  for  it. 

The  very  best  ears  of  seed  corn  are  planted  in  the  center  rows 
of  the  breeding  plot,  the  remainder  of  the  ears  being  planted  in  ap- 
proximately uniform  gradation  to  either  side,  so  that  the  least  de- 
sirable ears  among  the  40  are  planted  in  the  outside  rows;  and  in 
the  final  selection  of  the  best  field  rows  from  which  the  next  year's 
seed  ears  are  to  be  taken,  some  preference  is  given  to  the  rows 
near  the  center  of  the  plot. 

While  we  are  not  yet  ready  to  make  absolute  statements  re- 
garding the  matter,  nevertheless,  from  the  data  which  we  have 
secured,  and  are  securing  upon  the  subject,  we  now  recommend 
that  every  alternate  row  of  corn  in  the  breeding  plot  be  completely 
detasseled  before  the  pollen  matures  and  that  all  of  the  seed  corn 
to  be  taken  from  the  plot  be  selected  from  these  20  detasseled 
rows.  This  method  absolutely  prohibits  self-pollenation  or  close- 
pollenation  of  the  future  seed.  By  self-pollenation  is  meant  the 
transfer  of  pollen  from  the  male  flower  of  a  given  plant  to  the  fe- 


536  BULLETIN  NO.  82.  [December, 

male  flower  of  the  same  plant;  and  by  close-pollenation  is  meant 
the  transfer  of  pollen  from  the  male  flower  of  one  plant  to  the  fe- 
male flower  of  another  plant  in  the  same  row,  both  of  which  grew 
from  kernels  from  the  same  seed  ear. 

The  transfer  of  pollen  from  one  plant  to  another  plant  which 
grew  from  kernels  from  a  different  seed  ear,  we  term  cross-pollena- 
tion.  We  have  been  for  several  years  accumulating-  data  which 
show  that  artificial  self-pollenation  is  very  injurious  to  the  vitality 
and  vig-or  of  the  seed  produced,  and  we  have  also  secured  data 
pointing-  toward  an  injurious  effect  of  close-pollenation  even  by 
natural  methods,  so  that  we  feel  justified  in  recommending-,  at  least 
tentatively,  the  use  of  cross-pollenation  in  seed  corn  breeding-. 

It  is  also  recommended  that  in  the  20  rows  of  corn  which  are 
notdetasseled  no  plants  which  appear  imperfect,  dwarfed,  immature, 
barren,  or  otherwise  undesirable,  should  be  allowed  to  mature  pol- 
len. Detasseling-  is  accomplished  by  g-oing-  over  the  rows  two  or 
three  times  and  carefully  pulling-  out  the  tassels  as  they  appear. 

Occasionally  an  entire  row  is  detasseled  because  of  the  g-eneral 
inferiority  of  the  row  as  a  whole. 

FIELD  SELECTIONS  BASED  ON  PERFORMANCE  RECORDS. 

As  the  corn  crop  approaches  maturity  we  are  then  ready  for 
the  first  time  to  beg-in  at  the  real  beginning-  in  the  selection  of  seed 
corn;  that  is,  with  the  whole  corn  crop  and  the  whole  corn  plant, 
as  it  stands  in  the  field. 

We  then  make  our  first  selection  of  seed  corn  from  the  field 
rows  (each  of  which  is  the  progeny  of  a  separate  single  ear)  on 
the  basis  of  peformance  record.  Each  of  the  twenty  detasseled 
rows  is  carefully  examined.  Some  of  them  are  discarded  for  seed 
purposes  by  simple  inspection,  and  with  some  rows  this  decision 
may  be  made  early  in  the  growing-  season;  because,  when  each  field 
row  is  planted  from  a  separate  individual  ear,  that  row  has  an  in- 
dividuality which  in  many  cases  is  very  marked.  It  may  show 
very  imperfect  g-ermination  (in  the  most  careful  work  the  germi- 
nating- power  of  each  ear  is  ascertained  before  planting-),  it  may  be 
of  slow  growth,  produce  small  weak  plants,  or  numerous  barren 
stalks.  The  plants  may  be  tall  and  slender  or  very  thick  and  short. 
In  one  row  the  ears  may  be  borne  high  on  the  stalks,  while  in  the 
adjoining-  row  they  may  averag-e  one  or  two  feet  nearer  the  ground. 
One  row  may  yield  more  than  twice  as  much  corn  as  an  ad- 
joining- row  on  the  same  kind  of  soil.  As  a  matter  of  fact, 
when  one  begins  to  breed  corn  by  the  row  system  (one  seed  ear  to 
each  row),  he  is  usually  surprised  to  find  that  the  plants  in  some 


IQ02] 


METHODS   OF   CORN   BREEDING. 


537 


rows  are  so  very  different  from  those  in  others,  as  will  be  seen  from 
data  from  one  of  our  1901  breeding1  plots,  which  are  given 
in  Table  4. 

TABLE  4.     PERFORMANCE  RECORD  OF  BREEDING  PLOT,  1901. 
(Breeding  for  high  protein). 


Field  Row  No. 

Protein 
in 
seed  ear. 

Weight  of 
ear  corn 
in  crop. 

.x                

12.06 

91  .0 

2                       

12.  17 

86.0 

•3 

12.  IO 

98.5 

4..  .                                                     

12.26 

GO.  C 

c                                                                 

12.^1 

77.0 

I    :.:::  

I2.4O 

118.0 

7               

12.66 

116.O 

8               

12.  8^ 

54..  5 

9.  .... 

12.90 

107.0 

10         

15.78 

103.0 

II       

12.9^ 

87.0 

12            

I2.9O 

127.5 

I*                                                                

12.72 

113.  0 



I2.4i; 

123.5 

1C  .  .                                               

12.^2 

103.5 

li.::  

12.^1 

Q2.  0 

17 

12.23 

85.5 

18               

12.  l8 

117.0 

IQ                                                                                                                                             ,  .  . 

1  2.  07 

140.5 

2O                                           .  .                

12  06 

O7  o 

Average  

12.59 

101  .9 

We  take  no  seed  corn  from  a  row  which  produces  a  large  pro- 
portion of  imperfect  plants,  barren  stalks,  small  ears  or  a  low 
yield,  even  though  a  few  apparently  good  seed  ears  might  be  found 
in  the  crop  which  that  row  yields. 

The  points  to  be  considered  in  the  selection  of  the  field  rows, 
and  finally  in  the  individual  plants  from  which  seed  ears  may  be 
taken  should  include  the  per  cent,  of  "stand"  of  plants,  the  height 
and  physical  proportions  of  the  plant,  the  character  and  amount 
of  foliage,  the  position  of  the  ear  on  the  stalk,  the  length  and  size 
of  the  ear  shank,  the  per  cent,  of  ear-bearing-  plants,  the  time 
of  maturity,  the  total  yield  of  the  row,  the  average  weight  of  the 
ears,  and  the  number  of  good  seed  ears  which  the  row  produces. 

Some  of  these  points  can  be  determined  by  inspection;  some 
require  actual  counts  and  measurements  or  weights. 

The  corn  from  each  of  the  detasseled  rows  which  have  not 
been  rejected  by  inspection  is  now  harvested.  First,  all  of  the  ears 
on  a  row  which  appear  to  be  good  ears  and  which  are  borne  on 
good  plants  in  a  good  position  and  with  good  ear  shanks  and 
husks  are  harvested,  placed  in  a  bag  with  the  number  of  the  row, 
and  finally  weighed  together  with  the  remainder  of  the  crop  from 


538  BULLETIN  NO.  82.  [December, 

the  same  row.  The  total  weight  of  ear  corn  which  the  row  yields 
is  the  primary  factor  in  determining-  the  10  best  rows  from  which 
all  of  the  200  ears  for  the  next  year's  selection  must  be  taken;  and 
yet  no  corn  breeder  should  follow  even  this  rule  absolutely  or 
blindly.  If  it  should  happen  that  one  of  these  ten  best  yielding 
rows,  although  slightly  higher  in  yield,  is  nevertheless  plainly  in- 
ferior to  some  other  row  in  the  number  of  good  ears  produced,  the 
row  selection  should  be  changed  accordingly.  Yield  is  of  first  im- 
portance, but  it  should  not  exclude  all  other  points.  It  is  more 
practical  and  profitable  to  produce  99  pounds  of  good  ears  than 
100  pounds  of  nubbins.  Other  things  being  equal,  or  nearly  so, 
preference  is  also  given  to  the  rows  nearest  the  center  of  the  field, 
for  reasons  already  explained  and  well  illustrated  in  Table  4. 

In  the  final  selection  of  the  40  seed  ears  we  prefer  to  have  as 
many  as  possible  of  the  ten  best  field  rows  represented,  and  we  fre- 
quently sacrifice  slight  advantages  in  chemical  composition  for  the 
sake  of  having  such  a  large  representation,  because  of  the  possible 
future  evil  effects  of  too  close  in-breeding. 

Each  lot  of  20  ears  (more  or  less)  from  each  of  the  ten  best 
rows  and  finally  each  single  ear  of  the  40  seed  ears  ultimately  se- 
lected is  kept  labeled,  and  permanent  records  are  made  of  the  num- 
ber and  the  description  of  the  ear,  the  composition  of  the  grain, 
performance  record  of  the  row,  etc.,  so  that  as  the  breeding  is  con- 
tinued an  absolute  pedigree  is  established,  on  the  female  side,  for 
every  ear  of  corn  which  may  be  produced  from  this  seed  so  long 
as  the  records  are  made  and  preserved.  We  also  know  absolutely 
that  we  have  good  breeding  on  the  male  side  although  the  exact 
individual  pedigrees  of  the  males  cannot  be  known  and  recorded. 
The  corn  which  we  first  began  to  breed  (see  bulletin  No.  55,  Illi- 
nois Experiment  Station)  we  are  this  season  growing  in  fivedilfer- 
ent  breeding  plots  in  Illinois,  and  it  is  now  being  grown  in  two  or 
three  other  states;  and  every  ear  which  is  grown  this  year  in  any 
of  those  breeding  plots  has  an  established  and  recorded  pedigree 
for  seven  generations.  For  example,  each  of  the  ears  of  corn 
which  was  grown  the  past  season  in  our  high  protein  breeding  plot 
has  a  recorded  pedigree  showing  the  protein  content  of  its  dam,  of 
its  grand  dam,  of  its  great,  grand  dam,  of  its  great,  great,  grand 
dam,  of  its  great,  great,  great,  grand  dam,  and  its  great,  great, 
great,  great,  grand  dam. 

In  conclusion  let  me  say  that,  to  the  practical  corn  breeder,  I 
would  urge  only  three  things: 

First:    Adopt  the  row  system,  plant  20  to  40  good  seed  ears, 


IQO2.]  METHODS   OF   CORN   BREEDING.  539 

one  ear  to  a  row;  then  select  your  seed  for  the  next  year,  on  the 
basis  of  performance  record,  from  about  10  rows  which  produce 
the  highest  yield  and  the  best  ears. 

Second:  Breed  corn  for  a  purpose.  If  you  wish  to  feed  corn, 
breed  and  grow  high  protein  corn.  If  you  wish  to  grow  corn  for 
the  starch  and  glucose  factories,  breed  and  grow  corn  the  factory 
wants. 

Third:  Until  we  have  facts,  don't  devote  too  much  time  to 
"fancy  points,"  such  as  trying  to  produce  kernels  on  the  tip  end  of 
the  cob,  or  trying  to  reduce  the  size  of  the  cob,  or  trying  to  make 
the  tip  end  of  the  ear  as  large  as  the  butt,  or  pulling  out  suckers, 
or  doing  other  things  the  ultimate  effect  of  which  is  unknown.  It 
is  not  yet  known  with  any  degree  of  certainty  whether  such  things 
are  beneficial,  injurious,  or  without  effect,  on  the  production  of 
the  crop. 

And  don't  feel  that  you  can't  breed  corn  even  if  you  are  unable 
to  detassel  barren  stalks.  Last  year  we  had  fields  with  50  per 
cent,  of  barren  stalks, — this  year  in  some  fields  from  that  seed  we 
have  about  five-tenths  of  one  per  cent,  of  barren  stalks,  and  these 
examples  fairly  illustrate  the  tremenduous  effect  of  soil  and  season 
and  condition  of  growth,  as  compared  with  breeding,  upon  the  pro- 
duction of  barren  stalks.  Barren  stalks  bear  no  ears,  and  the 
whole  tendency  of  Nature's  Law  is  to  breed  them  out,  and  even 
without  the  intervention  of  man.  As  a  matter  of  fact,  in  order  to 
give  to  barren  stalks  an  equal  chance  with  ear-bearing  plants  to 
propagate  themselves,  we  should  be  obliged  to  detassel  every  ear- 
bearing  plant  in  the  field.  In  studying  this  problem  it  should  be 
borne  in  mind  that  the  female  parent  of  the  barren  stalk  was  not 
barren. 

It  is  probably  much  more  important  that  we  absolutely  pre- 
vent self-pollenation  and  close-pollenation  by  detasseling  alternate 
rows,  but  even  this  practice  is  still  an  experiment.  It  is  very  true 
that  exceedingly  poor  corn  has  been  produced  by  artificial  or  hand 
self-pollenation  but  recent  experiments  have  also  shown  that  corn 
may  be  degenerated  by  artificial  cross-pollenation;  and  it  should 
be  understood  that  our  recommendation  to  detassel  alternate  rows 
in  the  breeding  plot  is  tentative,  and  I  certainly  would  not  urge 
this  practice.  Probably  such  detasseling  will  prove  somewhat 
helpful  to  the  corn  breeder,  but  we  know  that  very  great  improve- 
ment can  be  made  without  detasseling  at  all,  simply  by  selecting 
seed  on  the  basis  of  performance  record  and  for  desirable  quality 
or  composition. 


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